1. Field of the Invention
The present invention relates to a semiconductor wafer basket for containing wafers having a detachable wafer press means provided underneath the top lid of the wafer basket.
2. Description of the Prior Art
Semiconductor wafers to be made into substrates for semiconductor electronic devices are obtained by thinly slicing a single crystal ingot of a semiconductor material such as silicon in a direction substantially perpendicular to the axis of the ingot. Thus, a semiconductor wafer is thin and fragile; besides, it need be kept clean from any contamination. Hence, transportation of wafers requires a great care and caution.
For this reason, it was a conventionally adopted practice to place wafers in a row at regular intervals in a wafer basket and transport the wafers in the basket. A wafer basket is a box-like rack for containing semiconductor wafers, and is commonly molded integrally of a synthetic resin. In construction the wafer basket comprises numerous shelves for receiving wafers in a row, each shelf consisting of a groove defined by a pair of neighboring partition ribs which ribs are formed at regular intervals. The wafer basket is also a vehicle means for transporting the wafers it contains. FIG. 19 shows a front view of an example of such conventional wafer basket, partially broken for a better view of its inside. This wafer basket consists of an outer box 101 and an inner box 102, and a plurality of wafers W are each received in the respective grooves defined by and between partition ribs which form the pleated side walls 102a, 102b of the inner box 102, which are facing each other; therefore, the wafers are placed in a row perpendicular to the sheet of FIG. 19 at regular intervals in the inner box 102. Also, a wafer press means 103, consisting of a plurality of resilient press strips each having an engagement groove, is detachably attached to the inside face of the top lid 101B of the outer box 101, and when the lid is placed to close the wafer container, as shown in FIG. 19, the upper edges of the wafers W stored in the inner box 102 are caught in the engagement grooves and thereby depress the respective resilient press strips of the wafer press means 103, which in turn resiliently biases the wafers downward so that when the wafer container receives a shock during a transportation, the wafer press means 103 absorbs the shock and prevents the wafers from shaking and thus incurring a damage.
However, such conventional wafer press means as shown in FIG. 19 is liable to rub itself against the wafers' edges as the wafer container receives a shock, and thus the wafer press means is ground and produces particles which contaminate the wafers W.
Also, the wafer W itself incurs damages as it is rubbed repeatedly by the wafer press means 103.
Furthermore, there is a problem with the conventional wafer baskets that when the wafers W are stored in the wafer basket and the top lid 101B is fitted on the outer box 101, some of the wafers W may fail to be caught in the engagement grooves of the respective resilient press strips of the wafer press means 103 but slip into gaps between the press strips; such dislocated wafers are loosely seated in the basket and are liable to damage themselves from transportation shocks and they rub themselves against the press strips to create contaminator particles.
The present invention was made in view of the above problems, and it is, therefore, an object of the invention to provide a wafer basket wherein the wafer press means is so constructed that there occurs scarce rubbing between the wafer and the press means which may create particles, and that the wafers in the wafer basket do not miss the grooves of the respective press strips of the wafer press means as the top lid is fitted on the outer box, so that all the wafers are resiliently pressed by the shock-absorbing press means.